Heat responsive switching devices

ABSTRACT

This thermal switching device is intended for switching a circuit with different time periods for the opening and closing thereof and is characterized in that it consists of a conducting wire having a relatively substantial coefficient of thermal elongation, said wire being connected at one end to a switch and at the other end to one end of a flexible blade carrying at this end a contact adapted to engage another contact connected via a first resistor to ground and at the other end through a second resistor of considerably greater value than the first resistor to ground, said blade further comprising a link actuating a movable blade contact adapted to open or close through a switch the circuit to be switched.

United States Patent [191 Rouvre et al.

[111 3,739,314 [4 1 June 12, 1973 .[22]. Filed:

[ HEAT RESPONSIVE SWITCHING DEVICES T [73]. Assignee: Regie Nationate Des Usines Renault,

Paris, France Sept. 17, 1971 [21] Appl. No.: 181,473

[30] Foreign Application Priority Data Sept. 23, 1970 France 7034460 [52] US. Cl. 337/395, 337/140 [51] Int. Cl. I-I0lh 37/50 [58] Field of Search 337/140, 395;

' BIS/DIG. 2

[56] References Cited UNITED STATES PATENTS 3,166,655 1/1965 Kline 337/140 X FOREIGN PATENTS 0R APPLICATIONS 703,308 2/1954 Great Britain 337/140 Primary Examiner-Hemard Gilheany Assistant Examiner-F. E. Bell Attorney-Stevens, David, Miller & Mosher [57] ABSTRACT This thermal switching device is intended for switching a circuit with different time periods for the opening and closing thereof and is characterized in that it consists of a conducting wire having a relatively substantial coefficient of thermal elongation, said wire being connected at one end to a switch and at the other end to one end of a flexible blade carrying at this end a contact adapted to engage another contact connected via a first resistor to ground and at the other end through a second resistor of considerably greater value than the first resistor to ground, said blade further comprising a link actuating a movable blade contact adapted to open or close through a switch the circuit to be switched.

2 Claims, 3 Drawing Figures PAIENIED Jmn 2191s saw a or 2 The present invention relates to thermal devices for switching electric circuits and has specific reference to devices of this character which are intended for switching a circuit with different closing and opening time periods. t

This type of device is applicable notably but not exclusively to combined control circuits of windscreen washers and windscreen wipers of automotive vehicles.

It is known that for cleaning a windscreen it is desirably to actuate firstly the windscreen washer, then, after a short time period, the windscreen wiper while allowing the windscreen wiper to operate during a few seconds after the windscreen washer operation has ceased. This result, with different timings for the opening and closing, has already been obtained through certain known devices, notably that described and illustrated in the French Pat. No. 69/26857 filed on Aug. 5, 1969 for Switching time-lag device, by the same Applicants which discloses a device combining the action of a heating wirewith that of an electromagnet and a bimetallic strip of the heating-wire type.

However, these devices are objectionable because it is necessary to wait until the windscreen wiper returns to its inoperative or initial position before operating again the windscreen washer and cause the release of another cycle of operation.

It is the essential object of the present invention to provide heat-responsive or thermal switching device characterized essentially in that it is free of the inconvenience set forth hereinabove, and that its cycle can be repeated without having to wait until the controlled circuit has resumed its inoperative or initial condition or position.

According to this invention, the deviceconstituting the subject-matter thereof comprises a conducting heating wire having a relatively substantial coefficient of thermal elongation, which is connectedat one end to a switch and at the other end to one end of a flexible blade carrying at the same end a contact adapted to engage another contact connected via a first resistor to a return conductor (ground), the other end of this blade being connected via another resistor of considerably higher resistance value than said first resistor to a return conductor, said blade further comprising a levercontrolling a movable arm adapted through. adequate circuit will now be described in detail by way v of exampie with reference to the attached drawing, in which:

FIG. 1 is a diagrammatic view showing the basic principle of' the device; a I FIG. 2 is a section showing a specific form of embodiment of the device of FIG. 1, and

FIG. 3 illustrates the wiring diagram in which the'device of this invention is incorporated in a windscreen washer and windscreen wiper control system.

Referring first to the diagram of FIG. 1, it will be seen that the device of this invention comprises a so-called. heating wire" or resistive wire 1 having one end connected to a fixed point of a circuit 1 and the other end. connected to one end of a flexible blade having its opposite end grounded through a relatively high resistance resistor 2. The end of blade 5 attached tothe heating wire 1 carries a contact 3 adapted to engage an-- other contact 4 grounded through another resistorl2 having a lower resistance than resistor 2. Blade 5 carries a link 6 also visible in FIG. 2, which is made of non-electroconductive material. The function of this link 6 is to provide a mechanical coupling between the flexible blade 5 and a lever 7. This lever 7 comprises a fixed point at one end and engages with its other end a rolling spring 8 having two stable positions. This spring 8 actuates in turn a contact-bearing lever 9 adapted torock between the pair of contacts 10, 11 of a switch inserted in a circuit II.

When no current flows through the wire 1 the assembly is in its inoperative condition, the forces involved being directed as shown by the arrows a in FIG. 1, the contact-bearing lever 9 engaging the lower contact 10. When current flows through the wire 1 the latter is heated and expands; thus, the lever 7 and blade 5 interconnected through the link 6 move in the directions of the arrows b, so that the contact-bearing lever 9 enis lowered and bears upon the lever 7which, through the medium of the rocking spring 8; lifts the contactbearing lever 9for engagement with the upper contact 11.

Also in FIG. 3'the same reference numerals are used for designating the corresponding component elements of FIG. 1; FIG. 3 illustrates diagrammaticallythe circuit of an assembly A comprising a windscreen wiper having a permanent-magnet motor adapted" to be stopped in anunvariableposition' also referred to as the fixed position, a windscreen wiper switch B, a windscreen washer pump C, and a timing device D adapted toextend the operating time of the windscreen wiper subsequent-to. the operation of the windscreen washer pump. v t

Referring to FIG. 3it will be seen that'the windscreen wiper'motor IS-comprises three terminals: 1

a grounded terminal 16 connectedon the other hand to one terminal 17 engageable by the movable contact arm 18 of the fixed stop switch, the other terminal 20 of thisswitch being connected tothepositiveter'minal 21' of the source of current-and also to'the aforesaid contact 11 co-acting with the contact-bearinglever 9;

terminals'2'2" and'23" connected to the high and low speed contact studs 24' and 25, respectively, of switch B.

This switch B comprises, in addition to contact studs 24'and 25, a contact'stud 26 connectedto the positive terminal-of thesource of current and a contact stud'27 connected to'the'lever'7. A sliding contact 28' permits connectingthe high-speed contact studs 24' and2 6 to thelow-speedcontact studs 25 and 26, or ZSand 27 (OFF position).

The time-lag device D comprises the abovedescribed component elements, namely the heating 3;. and a conductor 31 connectingthe terminal 32 of said pu'mp'to the heating wire 1.

ln th'e inoperative or OFF position the armature of the windscreen wiper motor 15 is short-circuited by the sliding contact in position 25-27, through lever 7, contact 10, fixed stop contact 18, and grounding terminal 16.

In the operative position of windscreen washer C the operator, for example the driver of the vehicle, depresses the push-button 30, thus starting the operation of :the washer pump 29 and causing the wire 1 to be heated rapidly. A current adjusted to a high value by resistor 12 flows through this wire 1 and the latter is thus elongated to unstress the flexible blade 5, and open contacts 3 and 4; the current flowing from this blade 5 to ground via resistor 2, the current assuming underlthese conditions a low value sufficient however to keep the wire 1 in this heated condition; by so expanding the flexible blade 5 actuates through link 6 to the lever 7, and when the over-center position of spring 8 is attained the contact-bearing lever 9 switches from contact 10 to contact 1 1, whereby the windscreen wiper motor is no longer short-circuited but energized. As long as the push-button 30 is depressed, the circuit is closed, the windscreen washer pump motor is energized, the time-lag blade 5 remains expanded and the windscreen wiper motor continues to operatepWhen the push-button 30 is released, the pump is stopped, the heating wire 1 being deenergized is cooled by the surrounding atmosphere and therefore contracts slowly during a predetermined time period. At the end of this time period the flexible blade 5 resumes its initial position, contacts 3 and 4 are re-closed, lever 10 is pulled through link 6, and as the over-center position of rocking spring 8 is attained the contact-bearing lever 9 reengages contact 10; as long as the fixed stop movable contact arm 18 engages the fixed contact 20, the windscreen wiper motor remains energized, and when the fixed stop switch re-opens the circuit the braked motor resumes its predetermined inoperative position.

The complete assembly is thus ready to start another cycle of operation which is obtained by depressing again pushbutton 30, and this can be done without waiting for the windscreen wiper motor to resume its inoperative position.

Of course, various modifications and variations may be made without departing from the scope of the invention as set forth in the appended claims.

What is claimed as new is:

1. A thermal switching device for switching a circuit with different opening and closing time periods, characterizedin that it comprises a heating wire having a relatively substantial thermal elongation coet'ficient, said wire having one end connected to a switch and the other end connected to one end of a flexible blade carrying at this end a contact adapted to engage another contact connected in turn via a first resistor to a return or ground conductor, said flexible blade having its other end connected via another resistor of substantially greater value than said first resistor to a return or ground conductor, said blade being also associated with a link controlling the position of a movable lever adapted to open or close the circuit to be switched through a snap-action contact.

2. In a combined windscreen-washer and windscreenwiper circuit, the use of the thermal switching device set forth in claim 1, characterized in that the heating wire is connected to the energizing circuit of the windscreen washer motor so as to be energized simultaneously therewith, the windscreen wiper motor circuit being controlled through the movable link actuated as a consequence of the elongation of the heated wire, said first resistor causing the rapid heating of said wire and a rapid actuation of said windscreen wiper motor, the second resistor keeping the wire in its elongated condition, the cooling of said wire by the surrounding atmosphere causing the windscreen wiper to resume its inoperative condition after a longer time period. 

1. A thermal switching device for switching a circuit with different opening and closing time periods, characterized in that it comprises a heating wire having a relatively substantial thermal elongation coefficient, said wire having one end connected to a switch and the other end connected to one end of a flexible blade carrying at this end a contact adapted to engage another contact connected in turn via a first resistor to a return or ground conductor, said flexible blade having its other end connected via another resistor of substantially greater value than said first resistor to a return or ground conductor, said blade being also associated with a link controlling the position of a movable lever adapted to open or close the circuit to be switched through a snap-action contact.
 2. In a combined windscreen-washer and windscreen-wiper circuit, the use of the thermal switching device set forth in claim 1, characterized in that the heating wire is connected to the energizing circuit of the windscreen washer motor so as to be energized simultaneously therewith, the windscreen wiper motor circuit being controlled through the movable link actuated as a consequence of the elongation of the heated wire, said first resistor causing the rapid heating of said wire and a rapid actuation of said windscreen wiper motor, the second resistor keeping the wire in its elongated condition, the cooling of said wire by the surrounding atmosphere causing the windscreen wiper to resume its inopErative condition after a longer time period. 